Why wouldn't you put them both centered on the wall? You don't say what size fireplace you are getting but once you get the firebox installed and stone/tile around it you will probably close to 7 feet for any reasonably sized fireplace. If I did the fireplace on the side with very little tile around it, I would use the other side for a tall shelf and still center the TV above the FP. Personally I don't think putting a TV above a heat source is a good idea, but that probably depends on how much you use the fireplace. If you have the fireplace picked out or any drawings of what you are thinking about, post them here so more people can help you. The more details you can offer the better feedback you will get.

The architect did you no favors when designing that wall. Even before I read the previous responses, I was thinking much the same thing--sheetrock over the niche and visually minimize the basement door. I went looking for an old post on concealed doors. This isn't the one I was thinking of, but covers the same territory: https://www.houzz.com/discussions/2523382/making-a-utility-door-disappear#n=7 Basically, you can replace the door with something with no trim, painted the same color as the wall that will completely blend it. It won't be truly hidden, since you will still see the outlines of the door, but it will be much less obtrusive than what you have now, and will let your fireplace be the focal point it ought to be.

Nicki, the sky is the limit there... you can do anything you like and there're so many options with all that wall space that you have. What look are you after and what materials would you like incorporate into your design? What is the budget you have in mind for that area that will play a huge role? The best way to start is to find an image with a fireplace wall design something that you after and you can work from there and make changes. Just to give you an example/idea I did a design for someone a while back just to give you an idea, in your case, the ceiling is taller, so you add few more shelves above the main mantle line, etc, or a set of built-ins,etc Good luck

I could post 100 pictures of what to do w/that wall. All depends on what you want to spend, if you want to keep the brick, remove the hearth, add windows, or shelving. since it faces north, you could bring in a few windows, or one on one side. put the tv on the large wall. have you looked at any inspriation pictures to give us an idea? light / coastal doesn't tell us a whole lot. you could remove that one wall, open it up, cover your beams (beam) with wood veneer (or strip the white) and bring in doors, or you could do taller windows to get this look: The brick is already there. just paint it white and add a wood beam mantle. replace fan w/a nice chandelier. if you do this, you could put tv on the FP. doors too much? here's a shot w/windows. this could work. shiplap around the brick, black stone around the box, windows, bench seating w/cabinets, reclaimed wood beams. just a diff design element. I would do these deep cabinets. you could do smaller windows w/floating shelves and a simple base cabinet underneath them. I like the idea of doing the fireplace w/something like this, windows, benches. love the dark blue too No windows. you could apply this millwork board and batten type of molding around the upper part of the brick. paint the lower brick. reclaimed wood mantle. for the side walls, built in bench, sconces. similar here w/this one. but no brick. The wood beams are beautiful w/your type of ceiling. you want builtins on the sides? do something like this. board and batten wood treatment on the upper portion, marble slab surround the firebox. start looking at fireplace wall design w/coastal decor. Or, vaulted planked ceiling with brick fireplace. you need to narrow things down a bit.